LATE PALEOZOIC SUBALKALINE POTASSIC (SHOSHONITE-LATITE) MAGMATISM IN CENTRAL TIEN SHAN

Magmatic associations of the shoshonite-latite geochemical type are abundant in epi-Caledonian structures of Central Tien Shan. They are concentrated along long-lived abyssal faults and form a narrow, elongate zone located near a marginal intercontinental rift created during Hercynian tectonomagmatic activation synchronous with orogenic processes in the Southern Tien Shan geosynclinal zone. The rocks belong to a gabbromonzonite (syenite)-granite association, sometimes with shoshonite, latite, and potassic dacite proper. Evolution of the magmatic systems involved magmagenesis in deep-seated chambers by partial melting of metasomatized mantle, formation of sialic magmas in intermediate chambers at crustal levels, possible mixing of mantle and crustal melts, and final emplacement primarily under hypabyssal and subvolcanic conditions.